org.terrier.matching.models.aftereffect
Class AfterEffect

java.lang.Object
  org.terrier.matching.models.aftereffect.AfterEffect

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

B, L, L5, LL

public abstract class AfterEffect
extends java.lang.Object
implements java.io.Serializable

This class provides a contract for implementing the first normalisation by after effect models for the DFR framework. This is referred to as the component (1-prob2) in the DFR framework. Classes implementing this interface are used by the DFRWeightingModel.

Author:

Ben He

See Also:

DFRWeightingModel, Serialized Form

Field Summary

protected double	avl The average document length in collection.
protected double	parameter The term frequency normalisation parameter used for method L5

Constructor Summary

AfterEffect()
A default constructor

Method Summary

abstract double	gain(double tf, double documentFrequency, double termFrequency) This method provides the contract for implementing first normalisation by after effect.
abstract java.lang.String	getInfo() Returns the name of the model.
double	getParameter()
void	setAverageDocumentLength(double value) Set the average document length, which is used for computing the prior for the first normalisation.
void	setParameter(double _parameter)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

avl

protected double avl

The average document length in collection.

parameter

protected double parameter

The term frequency normalisation parameter used for method L5

Constructor Detail

AfterEffect

public AfterEffect()

A default constructor

Method Detail

setAverageDocumentLength

public void setAverageDocumentLength(double value)

Set the average document length, which is used for computing the prior for the first normalisation.

Parameters:

value - The average document length.

getParameter

public double getParameter()

Returns:

the term frequency normalisation parameter

setParameter

public void setParameter(double _parameter)

Parameters:

_parameter - the term frequency normalisation parameter value to set

getInfo

public abstract java.lang.String getInfo()

Returns the name of the model.

Returns:

java.lang.String

gain

public abstract double gain(double tf,
                            double documentFrequency,
                            double termFrequency)

This method provides the contract for implementing first normalisation by after effect.

Parameters:

tf - The term frequency in the document

documentFrequency - The document frequency of the given query term

termFrequency - The frequency of the given term in the whole collection.

Returns:

The gain of having one more occurrence of the query term.